1. Field of the Invention
The present invention relates in general to a resilient support structure which is employed in a vibration system as in an automotive vehicle, for damping and isolating vibrations. More particularly, the invention is concerned with a fluid-filled resilient support structure which is adapted primarily for damping and isolating vibrations in the axial direction of the structure, and which uses a resilient member for isolating the vibrations through its elastic deformation, and an incompressible fluid for damping the vibrations due to a resistance to a flow of the fluid through an orifice formed in the structure.
2. Discussion of the Prior Art
As resilient support structures used in vibration systems as in a motor vehicle, for damping and isolating vibrations, there are known strut mounts and member mounts installed in a suspension system of the vehicle. Such conventional resilient support structures employ a cylindrical resilient or elastic member, alone or in combination with another member formed of a synthetic resin or canvas, for damping and isolating vibrations by means of elastic deformation of the resilient member. In this type of resilient support structure which relies on elastic deformation of a resilient member for damping and isolating vibrations, increasing the dynamic spring rate or constant of the resilient member for improved vibration isolating effect for reduced high-frequency vibrations and noises will unfavorably result in an increase in the loss factor of the resilient member, which reduces the damping effect for low-frequency vibrations or oscillations.
In the light of the above inconvenience, a fluid-filled resilient support structure is proposed in Publications Nos. 48-36151 and 52-16554 of Japanese Patent Applications, which were published for opposition purpose in 1973 and 1977. The proposed support structure utilizes an incompressible fluid to provide an improved vibration damping effect based on a resistance of flow of the fluid through an orifice formed in the structure. This type of fluid-filled resilient support structure utilizing elastic deformation of a resilient member and a flow resistance of an incompressible fluid is excellent in terms of its vibration damping capability as well as its vibration isolating capability. However, the fluid-filled resilient support structure disclosed in the above-identified documents is constructed primarily for isolating and damping vibrations that are applied to the structure in the radial direction of the resilient member. Hence, it is difficult to use the proposed support structure as a strut mount or a member mount, wherein major vibrations to be damped and isolated are applied in the axial direction of the resilient member.
In the meantime, such a fluid-filled resilient support structure adapted to damp and isolate the axial vibrations is disclosed in Laid-Open Publication No. 59-37348 of Japanese Patent Application.
However, the support structure disclosed in the above document suffers from a drawback that two identical units must be used as a set of support structures when the support structure is installed in place. Further, each unit is considerably complicated in construction, having a plurality of pockets or voids which are formed in each of the inner and outer surfaces of a resilient rubber member, such that the voids are spaced from each other in the circumferential direction of the rubber member. Accordingly, this known support structure is not completely satisfactory in ease of manufacture, assembling and installation, and is therefore undesirable in terms of its costs of production and installation.